Automatic telephone answering and message-recording system



July 26, 1960 w. J. BROWN ETAL AUTOMATIC TELEPHONE ANswERING AND MESSAGE-RECORDING SYSTEM v Filed April 2, 1958 5 Sheets-Sheet 1 Illlllll WJ. BROWN INVENTORS RJ. MILLER ByC/4. TAR/S ,ffm

July 26, 1960 w. J. BROWN ETAI- AUTOMATIC TELEPHONE ANSWERING AND MESSAGE-RECORDING SYSTEM 5 Sheets-Sheet 2 Fild April 2, 1958 ATTORNEY 5 Sheets-Sheet 3 w. J. a'RowN EVAL AUTOMATIC TELEPHONE ANSWERTNG AND MESSAGE-RECORDI/NG SYSTEM July 26, 1960 Filed April 2, 1958 ATTORNE Y July 26, 1960 w. J. BROWN ETAI- AUTOMATIC TELEPHONE ANSWERING -AND MESSAGE-RECORDING SYSTEM A 5 Sheets-Sheet 4 Filed April 2, 1958 ASSE Q.

u mviv 23% moua Tml` .W J. BROWN /NVEA/ TORS RA. MILLER Bye/v. TAR/s ATTORNEY July 26, 1960 w. .1. BROWN ETAI- 2,946,852

AUTOMATIC TELEPHONE ANSWERING AND MESSAGE-RECORDING SYSTEM l5 Sheets-Sheet 5 Filed April 2, 1958 Q wh.

' WJ. BROWN /NVENTORS RA. MILLER Bye. TAR/s WJ? m ATTORNEY nited AStates AUTOMATIC TELEPHONE ANSWERING AND MESSAGE-RECORDING SYSTEM William J. Brown, Madison, Robert A. Miller, Plainfield, and Charles M. Taris, Cranford, N J., assignors to Bell Telephone Laboratories, Incorporated, New York N.Y., a corporation of New York Filed Apr. 2, 1958, Ser. No. 725,941

28 Claims. (Cl. 179'6) calling party disconnect by absence of speech on thev telephone line for a predetermined length of time or by.

interruption of telephone line current.

An object of this invention is to'provide a telephone answering and message-recording system in which the length of the incoming message is determined by the caller, and is limited only by the maximum capacity of the record medium of the incoming message recorder.

Another object of this invention is to provide a telephone answering and message-recording system which includes facilities for providing the caller with aural indications when he pauses for a predetermined length of time, to indicate that he is still connected to the messagerecording system, when the level of his incoming message is Ibelow an acceptable minimum amplitude and when he is to be disconnected from the incoming message recorder as a consequence of low speech level, absence of speech or trouble in the message recording system. The aural indications are in the forms of steadystate audio frequency tone, tone beeps and playback of the last part of the message-recording.

A further object of this invention is to provide atelcphone answering and message-recording system which includes facilities for enabling the subscriber tomonitor the telephone line at any time without interrupting automatic operation, to break in on a call during automatic answering and during the recording of the incoming message, and to originate a call and the subsequent 'automatic incoming message-recording cycle.

In accordance with this invention, the above-noted objectives are satisfactorily met by a system comprising an automatic telephone answering set of the type disclosed in patent application Serial No. 493,722, filed by C. R. Keith, C. A. Nickerson and C. M. Taris on March 11, 1955, now U.S. Patent 2,846,505, issued August 5, 1958, an incoming message recorder of the dictating machine type produced for commercial use by a number of manufacturers, and a control unit by means of which the components of the system are tied together and connected to the subscribers telephone line.

The features of the invention reside primarilyin the control unit which contains all the equipment necessary to integrate the yother components into the system and to connect them to the telephone plant. Besides relay control circuits, the control unit contains a warning-tone oscillator, telephone line speech amplifiers and voiceoperated calling party disconnect facilities. The -voicecontrolled circuits of thecontrol unit'are energized directly by speech on the telephone line. f

4An incoming call activates the telephone answering arent (about 1/2 second in duration) on the telephone line,`

ice

set and the pre-recorded announcement is transmitted to thev caller in the normal manner. At the end of the announcement, the control unit (referred tov hereinafter as CU) switches'the caller to the incoming message recorder (referred to hereinafter as IMR). At the same time thevCU puts ak single, high level, MOO-cycle, beep followed immediately by a constant amplitude, low level, l'400-cycle tone.y

The callers message is recorded by the IMR.' lf he speaks loudly enough, the constant amplitude tone. (the talk-down tone). will `disappear completely. If he pauses for more than about two seconds or his voice drops below a certain level, the talk-down tone reappears on the telephone line. The caller is instructed -by the announcement or has previous knowledge that in order to leave an acceptable message he must talk down the tone. The talk-down tone also serves as an aural indicator for the caller.l It informs him that he is still connected to the.

IMR and that the recording process is still operative.

If the caller ceases speaking for an interval more than about ten seconds long (the last eight seconds of which will have talk-down-tone), a series (four `or more) of high level, MOO-cycle beeps will be transmitted to him by the CU. After this warning beep interval of about iive seconds, the talk-down tone reappears for an addi-v4 tional two seconds. Unless the caller speaks before this time-out cycle of about seventeen seconds is completed, the CU will disconnect from the telephone line. By

speaking a word or two the caller may interrupt the timeout cycle at any time, even during the Warning beep interval. Once the time-out cycle isinterrupted it reverts to its starting point. f

. The CU will time out a call on the lbasis of whether o r not speech, at adequate level, is presenton the telephone line. Control is achieved by. using the syllabic frequency of normal speech (below about ten cycles per second) rather than ythe audio frequencies. TheI callers speech is amplied and rectified. The audio components of the rectified speech are then filtered and the syllabic modulation components (sub-audio components) of the speech transmission, corresponding to syllables, words, groups of words and pauses between them, are used to energize relays which control the time-.out and tone talk-down facilities. The voice control used in this system avoids false Voperationv due to power line noise,

dial tone and the like because of its inherent insensitivity to steady-state audio frequencies. The voice control `s also made insensitive to telephone line'clicks and transients.

The subscriber can interrupt the IMR recording cycle. He may talk to the caller' and then reestablish the IMR recording cycle. As a consequence of this break-in feature, the subscriber can originate a call and, after the called party responds, start the operation of 'the IMR.-

The IMR recording cycle will proceed as it would have if the called party had originated the call.

The subscriber has the option of placing the system The subscriber is able to change'the"announcement of the answering set' during the time the IMR is recording an incoming message as well as during the inactive intervals of the system between incoming'calls.

The CU-will Yprovide pulses corresponding to the in- .terva1s,. in the recording cycle, during which speech is absent for more than two seconds. The IMR may use these signals to stop and start its record medium and thereby conserve recording material.

lhe CU also has facilities that enable it to recognize the operating status of the IMR and the telephone-answering set. Unless the IMRis pre-set for the record' functionandhas suflicientrecording time renfniinir'lgy on they recordinglmedium for a minimum incoming-n-less'agerrecording,v the incoming call. will not be accepted and unless the answerin'grse't is pre-set for automatic answer,- the callerv` will receive adont answer indication. In'addition,vr the CU will recognize a change in operating status of the" IMR" during the'message-recording cycle andvv disconnect' the caller from the system after transmitting'vadisconnect" signal: to hirn. Otherfdi'sco'nnect signals are7 also f gen-l erated by the CUfto notify the caller when the endofV IMK recording tirrie'is;aprroacl'lin'gv and when theV record. ingame'diumvis exhausted. Y A A 1 The nature of the invention and',` its distingui'shn'gjfeaturesand" advantages will be more' clearly understoodfr'om the following detailed' description and' the accompanying drawingsiin which:` v

Figs; l; 2', 3" and4,wl:ienv assembledV as' indicated in Fig; 5", constitute" a diagrammatic disclosure ofthe preferred embodiment of'theinventi'on, showing the'control unit and theinterconnections' between the units of the system. Fig'. 6V is a block` diagramV` of the invention'.

VIn'the' drawings, the relay contacts are shown detached from the relay windings'. Therst digit of'each referencev numberindicates' the` figure in'which it appears and the letters indicate the function thereof; Relay' 4PST, for.' example', is theme-*start relay and appears irr Fig. 4. TheA designation" of the contact ofA a relay includes in parentheses the relay' reference numberwith the lirst digit' before the parentheses'indicatingthe ligure in which the contactappears. Contacts 1(4P`ST)1 and 1(4PST)2, for example, appear in; Fig: l and' are contacts ofthe prestart relayI PST which appears in Fig. 4'; Contactswhich aree-closed when` the' relay is operated are represented by anl X crossing lines representing the connectingfconduct'ors.l Contactsxwhich'l arev opened when therelay isV operated are represented by a"-'.

' With the telephone-answering `set in automatic vanswer standbyV condition audits power supply 1PS activated, the-Crelay 4AA is operatedJ by voltage (48 volts) supplied' over the path'including',r conductor 10A, switch 481, closed contact 4(2D)1 of' relay 2D and conductor 4-^connected to" ground'. The' operation of relay 4AA completes -the CU telephoneline circuit to the' telephone answering set over the path includingy conductor T," closed contact 4(213'15'1,A of' relay ZBI, switch`4S1 and'operated contact '4('4AA)1' of "relay 4AA,` and the path including" conductor'Rf, 4(2,BD3 v switch 4S1 and operated'contact' 4(4A)2 of relay 41AA; Operation of relayv 4A also opens the telephone set ringer circuit (not shown) and closes Contact 4(4AA)3`in the operate circuit of 'start relays 4ST and-'4ST.

With the IM-R in condition for recording (power applied, record function enabled, recordings are* ydriven in position, minimum recording capacity available, etc.) relay 3IMR1-is operatedY by' rectified voltage supplied o'ver the path which includes the alternating currentoutput winding of power supply IPS, conductor 6, rectifier' 3X3k andV conductor 8 connected. to ground. Operation of relay 3lMR1U-cl'oses the` operate path ofrelay'SIMRIA, saidipath: including power supply lvPS, conductor 2,-op`- erated` contact 3(3IMR1!)1 of relay HMRIk and-closed contast 3-(3VOCS )1 of voice control relay 3VOC5.-

.With Vthe answer-andi record condition establishedthe l system is ready to accept an incoming calliA The subscribers vte'lephonelineis connected. toithe telephone answeringset via the CU, andringing current will go directly to' the set ring-up circuit over thepa'thi describedheretofore.' Ring-upl relay K2 (not shown) ofthe tele-A phoneanswering set responds'toL thel ringing current Yand operates contacty 4`('K2)"1 to" close Lthe operate path of 4. pre-start relay 4PST. Relay 4PST is operated by voltage supplied over the path to ground which includes conductors 2, 10 and 1-2, closed'contact 4(2AO)1 of relay ZAO, conductor 14, contact 4(K2)1 of relay K2, conductor 16 and closed contact 4(2AO)2 of relay 2AO.

Operation of relay 4PST prie-sets the .1MR and CU for Ythe incoming message-recording cycle. Operated contact' 3 (MEST) i1" closes a; circuit toterminals D' and` M of the lMK'whichcanbe' used" to warm up its amplifier', start theI drive, motor?, and the like.

voice-operated relay' SVOCS toy charge" fullyf andi closes Ythe operate circuit of'relaySVO'Cf Relay SVOC-S'iis the pre-recorded;announcement is transmittec to the' caller; At the'end ofthe-announcement, af contact on the adjustable limit switch (notl shown) ofthe'telephone" answering set'v closes*y momentarily; This? closure puts ground on terminal; 2 of" theH telephone answering set; Relayl4STA isthe'n operated' by' groundl provided over the" path which includes operated contact 4(4PST)1 of relay' 4PST, closed` contact 4(4ST)1 of relay 4ST"v operated contact 4(4PST)2 of relay 4PST, operated` con'- tact 4(3'I'MR1A)1v of relay 3'IMR1A and operated contact 4('4AA)3 oferelayl Operated4 contact 4(4STA) 1: of relay ASTA closes' thev operate path for relay 4ST. Operated-contact 3(4ST)1 andl closed contact 3(2BI)1 completes' the start' and disconnect signal-circuit 'to' terminalsE and M'of the IMR'. The4 IM-R record medium is" put into motionvand the recording cycle starts;

Operated contact 4(4S"l`A-)2rofV relayA 4S-TA closes the operatelpathf'of" telephone line holding relay K6 ofthe telephone answering set; tlie telephone* answeringset continues to hold the telephone" line'altlough the-remainderof the set isV restoredu tof standbycondition. The-delay in allowingfthe answer-` the- CU 'time'` to seize the linee' and take overline'-l holding: Operatedl contacts' 1*(4STA1)1V and 1(4STAJ2' ofrelay 4STA Bridge caIIingp'arty-CGntTOl relaylCPC across Ythe telephone line.

contactl 1(4PST)`1= andfseizesthe telephonefline; Oper- ReIayKG is therebyv deenergi'zed'and' the answering-set' immediatelyfdiops off` the`lr telephone line.' On operation A high. level", l400cycletone beep-nowappears-on the* The=` telephone line.v This*Y isA -thecallersf' start signal.A duration-"(l/z tol second) ofthe beep ,isco'ntrolledl primarily bythex release time of relay 4PST. The' tone generatorcomprising transistor1Q-1V is energized by voltagel supplied to the emitter-terminalfoverthe patl'r including closed-contacts 1(-2BI')1 and-1'(2O)`1, operated contact by resistors1K1, lR-'Sf and IRIS.' SwitchA SZfis provided? so* thatthe :start beep may bedisabled when the appearance of talk-down tone` is suicient signal--forthefcaller-to? start talking.

With the 'answering set'ofritheline anlrel'ayl K2 AVdeentonel is controlled byfresi'st'r 1K7 lwhich is Y'inthe-tmeV generator energizingU path including closed contacts Also, operated' contact' 3:('4PST.) 2 causes: the: timing: capaeiton 3G1- of A Relay'K6- remains operated andi Relay' ICPC operates vthrough operated 1(4ST)3 and closed contacts 1(3IMR2)'2, 1(3A)1 and 1(3VOC2A) 1 and switch 1S3. The release of relay 4PST also locks relay 4ST over the path including operated l contact 4(4ST) 1, resistors 4R33 and 4R34, operated contact 4(1CPC)2 and closed contact 4(2BI)2; removes the l prestart signal from the IMR at terminals D and M; releases relay 4STA and places time out relays 3VOC3 and 3VOC4 under direct control of the `voice-operated circuits. Relay 1CPC remains connectedacross the telephone line through its operated contact 1(1CPC)1.and'

be high enough in level to operate the voice-operated control circuits erroneously during transmission of the disconnect beeps (described hereinafter). The voice-operated circuits will not respond to the steady-state talk-down tone since they are sensitive only to sivnals which vary in amplitude at a very low rate, below approximately ten cycles per second. (For interrupted tone the 1400- cycle is eliminated from voice control circuits.) The talk-down tone will remain on the telephone line until the caller starts to talk. If his speech level is above -35 v.u., measured at CU terminals T and R, the tone will stop.

The callers speech reaches transformer 1T1 of the C U via operated contacts 1(4ST)1 and 1(4ST)2 and closed contacts 1(2Bl)2 and 1(2Bl)3. Capacitor ICS is provided to prevent telephone line current from flowing through winding 3--4 of transformer 1T1. The talkdown tone oscillator comprising transistor 1Q1 is also coupled to the telephone line by means of transformer 1T1. VBefore the callers speech reaches the IMR input terminals A and B it is amplified by the amplifier comprising transistor 1Q2. The callers speech is further amplified by the ampliiier comprising transistor 3Q3.

'Ihe amplified speech is rectified by varistors 3X1 and 6X2. Capacitor '3G13 iilters the audio components of the rectiiied speech. The sub-audio components of the speech transmission, corresponding to syllables, words or groups of words and pauses between them, charge capacitor 3G14 but allows it to discharge through 3X3, 3R22 and 3R21. Transistors 3Q4 and 3Q5 are biased to cut-off in the absence of a'charging current to 3C14. When the voltage across 3R22, due to the charging current, reaches a predetermined value, collector current starts to iiow. The transistor circuit parameters are so chosen that maximum collector current ows for a slight increase in voltage across 3R22 beyond the base-emitter bias voltage established by 3R23 and 3R37. Resistor 3R18 is adjusted so that the collector current of transistor 3Q4 is suicient to operate relay 3VOC1 when the speech level at terminals T and R just exceeds -45 v.u. The operate time of the entire speech control sequence, from terminals T and R to 3VOC1, is less than approximately 25 milliseconds. This is substantially independent of input level. Resistor 3R22 is adjusted so that the collector curf rent of transistor SQS is sufficient to operate relay 3VOC1A when the speech level at terminals T and R just exceeds 35 v.u. The operate time is substantially the same as for the 3Q4 sequence. The value of -35 v.u. was chosen arbitrarily for the embodiment being described. Resistor 3R22 can be adjusted to operate relay 3VOC1A at speech levels in excess of -45 v.u. to about -25 v.u. The voltage dividers, 3R24/3R26 and 3R25/ 3R27, serve to keep the collector-emitter voltage of 3Q4 and 3QS below the rated maximum value.Y Operate circuit of relay SVOCZ has slow-operate characteristics (about 75 milliseconds). 'Ihis makes it relatively insenstant of caller hang-up. False operation of the CU timeout circuits is thereby avoided.

The caller starts to speak as soon as he hears the talkdown tone. (The l400-cycle tone and beeps are attenuated by the ilter comprising network 1Z4 and 1R14 and by network 325 so that they will be apparent at terminals T: and R but not at IMR input terminals A and B or the voice-control circuits.) Let us assume that the callers speech level at terminals T and R is approximately -25 v.u. About 25 milliseconds after he starts to speak relays 3VOC1 and 3VOC1A operate. With contacts 3(3VOC1)1 and`3`(3VOC1A)1 operated, relays '3VOC2 and 3VOC-2A operate shortly thereafter. Normally closed contact 1(3VOC2*A)1 opens the power supply to the tone oscillator andV talk-down tone stops. Operated contact 3(3VOC2)1 causes capacitor '3C1 to recharge across the winding of relay 3VOC3, and energizes relay BVOCS. The time-out cycle is restored to its start condition. As long as the caller continues to speak at a level (at terminals T and R) above -35 v.u., both relays SVOCZ and '3VOC2A will remain operated. Relays SVOCI and 3VOC1A will chatter, that is, operate and release in response to words and pauses of suticient duration. Relays 3VOC2 and 3VOC2A will not follow relays 3VOC1 and 3VOC1A because of their long release time of approximately tWo seconds. This time is independent of speech level. 3(3VOC1A)1 charge capacitors 3C17 and 3C18 very rapidly but must remain open for more than two seconds in order forV these capacitors to discharge enough to release relays 3VOC2 and 3VOC2A. While relays 3VOC2 and SVOCZA are operated'the talk-down tone is oli; the time-out circuits are fully charged (relay 3VOC3 and 3VOC4 are operated). The IMR is notified of these conditions by the opening of circuit MF at contact 3(3VOC2)2 and the closing of circuit MG at contacts 3(3VOC2)3 and `3(3NOC302.

If the callers level drops to a value below -35 v.u., but remains above -45 v.u., relay 3VOC1 stays operated but relay 3VOC1A releases immediately. About two seconds later relay 3VOC2A releases, energizing the tone oscillator; talk-down tone appears on the telephone line. y

The presence of talk-down tone under these conditions will not effect the incoming message record cycle. The callers speech will be recorded normally (with perhaps 1400-cycle tone at very low level in the background); the time-out circuits will remain fully energized. The talkdown tone will remain until the callers voice level rises above -35 v.u. The differential in speech level for thev operation of the time-out and talk-down tone circuits (VOCl and VOC1A respectively) is provided because it is felt vthat the talk-down tone should advise the caller to speak louder before his speech level has dropped sufliciently to start the time-out cycle. Resistor 3R22 determines the operating point of the talk-down tone circuits. lf the shaft of potentiometer 3R22 is turned to the maximum clockwise position, talk-down tone will appear at the same time the time-out cycle starts; VOCI and VOClA Will both release when the speech level at terminals T and R drops below -45 v.u. If the callers speech level drops below -45 v.u. at terminals T and R, relay 3VOC1 will also release. Two seconds later relay SVOCZ releases. The CU time-out cycle commences. The IMR is notified by circuit opening MG and circuit closure MF. Reappearance of speech of adequate level on the telephone line, will cancel the time-out sequence and will remove the talk-down tone from the line. The appearance of talk-down tone is delayed two seconds after speech stops, for a Very definite reason. It is felt that an immediate appearance of tone would have an adverse psychological effect upon the caller.

Since the operate and release condition of the CU timey out relay SVOCZ is relayed to the IMR, the IMR can Operated contacts 3(3VOC1)1 and.

senceandpresence of-'speech (or speechof adequate level,`

long, pause. (longer than; two: seconds) and` the; responsetime. of thel voic'.e.operated. control'. circuits is.- appreciable: (about 100. milliseconds),- speecln clipping will occununtless the lMRhasprovis-ions for delayed recording; If the timefre'quiredfor thecallersspeech to-travel from the input terminals' (A and B9* toy the-l recording medium is greater than 100 milliseconds, say 1'50 mi l1iseconds-,.thcn.

the motion of theV medium could be controlledy by relay SVOCZ. Relay 3VO`C2 will not operate until 50 milliseconds after speech'- has appeared aty terminals T and R but the speechwill not reach the recording medium until 50 milliseconds `later-allowing 50 milliseconds for the necessaiy iMRf control switching and for the medium to` reachoperating speed Clipping of part of the callers rst word as he resumes talking will thereby be avoided.

The-caller has now finished his message and hangs up. If hang-up is accompanied by an interruption in telephone line current (such as would occur in a step-by-step area), relay CPC releases. Relay 4ST releases about l0 milliseconds later. The l-MR stops recording; theincorning message record cycle ends; the IMR and CU resume the answer and record standby condition, ready to accept another call.

if caller hang-up is not accompanied by a current interruption orif he'v ceases speaking, the CU starts to time out. The complete time-out sequence is as follows.

a. 50 milliseconds or so after speechA stops, relays 3VOC1 and 3VOC1A release. y

b. Two seconds later relays 3VOC2 and 3VOC2A release.

c. Talk-down tone appears. v

d. `Eight seconds later relay SYOCS releases and con tact 3(3VOC3 a closes.

e. Relays 3A and 3B start to function as a pulse generator. Relay SA operatesv and releases atV about a 1/2 second rate. Operated contact 1(3A)2 of relay 3A energizes the tone oscillator. Voltage is supplied'over the path including operated contact 1.(4ST)3 of relay 4ST, closed contacts 1(2BD1; of relay ZBI, 1(2AO)1, 1(5VOC6)1 and 1(3MR2)1 of relay SIMRZ, closed contact 1(4PST)2, operated contact 1(3VOC4)1 of relayV 3VOC4, resistor falco, andv network llZl'. The tone oscil lator generates lAOO-cyclevdisconnect beeps (about 1/2 second on, 1/2 second. olf). The beeps appear at terminals T and R at about -5 V.u. Talk-down tone is not disabled during the interval between successiveY beeps. The interval between successive beeps has been made a minimum of 300 milliseconds by choosing relaysSA and 3B with proper operate and release times. A minimum of 300 millisecondsis required to allow certain types of echo Suppressors on toll loops to unlock. Unless the echo suppressors aref given time to unlock, the caller cannot recapture control. (interruptv the time-out cycle) during transmission ofthe disconnect beeps.

f. Five seconds after 3VOC3 isreleased, 3VOC4 releases; a disconnect beepsstop; relays 3A and 3B are deenergized. Talkdown tone continues over the path including. closed contacts 1(3iM-R2)2, 1(3A) and 1(3VOC2A)1.

Yg. Relay 3VOC4 Contact 4(.3VOC4)1 across 4R33 and. 4G24 opens. Capacitor 4G24 starts to chargethrough relay` 4ST winding; relay 4ST remains operated. ln about two seconds, the. charging current drops toa value low enoughir. relayiST'to release.

. Release of relay 4ST terminates the incoming messagerecord cycle.; Simultaneously: talk-down. tone stops; telephone line current. through relay lfCPC stopsyhol'cling" termination ony the? telephone line is removed; the

start-disconnect circuit. (EM.) is' opened.` The IMRV and:

` CU resumethe answer and recordread-yf condition..

IMR-voce andrecord medium. motion alarm off. failure' of the record speech circuits or failure- Wherr troublez occurs'in the IMR, afcontact closure to ground at terminalE inthe record medium drive mechanism.

P operates relay 3VOCS andholds'it operated; Operation of relay 3VOC5 releases relayf SIMRIA to close contacts 3`(3IMR1A)1 and1(3IMR1A)1, to operaterelay 3A and'v to close contact 1(3A)2 and thereby initiate: thel CU time-outsequence consisting ofseventeen seconds of. dis'- connect beeps which the caller cannot talk down. After timeout, the system vwill gointo adont answer condi tion until the trouble iscorrected and relay .iN/'OCS'4 is released.

The chance of failure of the IMR record mediumV drive system isl perhaps greatest atV the start of the recording? cycle. However, since the CU cannot anticipate failure in the IMR, the recording cycle will always be initiated' first, then relay SVOCS will be allowed to determine whether or not the cycle should continue. It would be possible to arrange the control circuits to delay the start;

ofthe recording cycle until relay SVOCS gives ago-ahead l command, but thisV procedure is ruled out becauseit is possible, under certain conditions, to get the system into a locked-out condition for very long periodsl of' time.l Relay failure in the IMR could cause the locked-out condition during which the telephone line is seized but no and SVOCZA are deenergized.

End of recording medium warning signal' Another control signal that the IMR provides is the End of Recording Medium Warning Signal. The IMR is required to close this circuit by applying ground toy terminal S when from fteen to thirty seconds ofrecording medium remains. This circuit closure operates relay SIMRZ in the control unit. The control circuits arev s'o arranged that operation of SIMRZ closes contactsy 3(3IMR2)1` and 1(3IMR2)`3 and causes the talk-down tone to be interruptedwby pulse generator relay A, at the same rate as the disconnect beeps. The pulsing talkdown tone is distinguished from the disconnect beeps by the difference in level. The disconnect-beep will beat least 20 db higher in level.

Pulsing of the talk-down tone will continue until either the caller hangs up or the recording medium is exhausted. Thecallers speech will not stop the pulsing talk-down tone since the path for energizing the oscillator includes operatedcontacts 1(3A)1 and 1(3IMR2.)3,. and does not include contact 1(3VOC2A) 1. It is intended to. be. a

warning to the caller that the recording mediumis nearing,

exhaustion and that hed betterl prepare to terminate customer. All calls to the installation will-'getf afdont answer until relay 3IMRZ is released. The Dont Answer Alarm Signal Circuit to the IMR at terminalV C will be closed during this interval.

y Subscriber "break in so he interrupts the cycle in progress and is placed inl direct communication with the caller.. The subscriber can then give the caller appropriate instructions or take the message manually. If instead, the subscriber wants the incoming message recorder to resume recording the callers message, he merely depresses and releases the A-R reset and restart button shown in Fig. 2. On lifting the handset switch ZSW closes. On depressing the line pickup button relay ZBI operates and contacts 2(2.BI)1 and 2(2BI)2 close. The closure of contact 2(2BI) 1 operates relay 4PST. On depressing the reset and restart button ground is supplied over the path including operated contacts 2(2BI)2, K4(3IMR1A)1 and 4(4PST)2, closed contact 4(4ST)1 toreenergize relay- 4ST. An an ticipated application of this feature will now be described to illustrate the principles of operation.

A caller has reached the system and is in the process o f recording his message. message, the end of recording medium Warning sounds. The subscriber upon hearing or seeing the alarm indication lifts the telephone handset. The telephone set is connected so that he may monitor the telephone line without having to depress any of the telephone set buttons. At an appropriate place in the callers message, the' subscriber depresses ythe line pickup button. Relay ZBI inthe CU operates, contact 4(2BI)2 opens, relay 4ST is deenergized and the IMR is stopped. The voicefoperated control circuits and the IMR resume thel pre-start, standby condition. In order to prevent recording the conversation, the input speech circuit of the IMR is shorted and grounded. The subscriber tells the caller to hold on while he changes the recording medium. He lays the handset on the desk (not back of its cradle) and proceeds to install newy recording material in the IMR. During this time, the caller hears room noise to indicate that the connection is still made. When the new materialhas been installed, the subscriber returns to the telephone set and tells the caller to resume recording his message. As hespeaks the lastv mitted to the telephone line, at the end of which talk- 6 down tone appears.

message.

The subscriber monitors the telephone line after he has depressed the restart button to make certain the caller has understood and followed his instructions. if the caller does not respond properly, the subscriber can break in again and repeat hisV instructions. The break in technique may be employed as manyvtimes a's the subscriber iinds it is necessary, without any detrimenta eiects. l

The subscriber has only one precaution to observe- If he hangs upV after breaking into the recording cycle without'depressing the restart button, relay 4ST will not be reenengized and the CU will dropl oif the line. Subsequent calls will ring the telephone set'bell and will get The caller'resumes recording his and Before he has completed hisy a` dont answerr unless the subscriber or attendant answers the calls manually. v

As noted above relay ZBI operates directly from a contact closure established by locking of the line pickup button on the telephone set. Contacts on ZBI operate prestart relay 4PST; release start relay 4ST; ground the speech input circuits to the IMR; disable the tone gen erator; enable the restart circuit to start relays 4ST and 4STA; and disconnect the answering set from the line, if break-in occurs during'the announcement (answering) cycle instead of the IMR incoming message recording cycle (at opened contacts 4(2BI)11 and 4(2BD3).

The line pickup button is illuminated while it is in the locked position. Voltage is provided to the line pickupy lamp over the path lincluding operated contacts 2(2BI)3 and-closed contacts 2(2AO)1 and 2(2D)2. If the system is in a ready condition, the CU ready and IMR ready lamps also illuminate when the subscriber lifts the handset. The switch-hook and relay 4PST are used to enable the CU and IMR ready lamps during the time the line pickup button is depressed. Voltage is provided to the CU ready lamp over the path including operated contacts 2(74AA)12(3IMR1A)1 and 2(4PST)1l and closed contacts 2(2AO)1 and 2(2D)2. Voltageis provided to the IMR ready lamp over the path including operated contacts 2(3IMR1)1, closed contacts 2(3VOC5 )1, operated contact 2(4PST)1 and closed contacts 2(2.AO)1 and 2(2D)2. The subscriber or attendant is thereby continuously aware of the system status during the break-in procedure. If, for example, the IMR develops trouble during t-he time the subscriber is talking to the caller, the IMR ready lamp will extinguish advising him that he cannot restart the record cycle and must therefore inform the caller accordingly. Although the CU ready lamp will extinguish once the IMR record cycle resumes, the line pickup button will remain illumi nated during the entire interval the button is depressed. The line pickup lamp is a condition-indicating or warning lamp; the caller will get -a dont answer during the. interval the line pickup button is depressed, even though' the CU and IMR ready lamps are on. Consequently, a dont answer alarm is established by the CU for the line pickup condition.

The control circuit arrangement in the CU which permits break-in also permits the subscriber to originate a call yand subsequently initiate the IMR record cycle. He may do this by depressing the line pickup button and dialing the called partys number. When the called party responds, the customer issues the proper instructions and operates the A-R reset and restart button; the called party then records his message. Once two-way communication has been established, the CU will respond to the restart signal in the manner described above for the break-in procedure. The CU has no way of determining who originated the call once relay ZBI operates.

Answer only y If. for some reason the subscriber wants to disable the recording portion of the system but wants the callers to receive appropriate instructions, he sets up the answer only function. He does this simply by recording the appropriate announcement on the answering set and then.

depressing the answer only button on the telephone set (shown in Fig. 2).

A contact on the answer only button operates relay 2AO in the control unit. 'Relay ZAO then performsthe necessary switching to establish the answerl only function. Relay ZAO disables the voice-operated circuits .at opened contact 1(2AO)1; opens the operate path of prelstart relay 4PST; closes the Dont Answer alarm signal circuit to the IMR by operating contact 3(2AO)|1. Since the answer only function may be utilized during periods when the IMR is inoperative, contacts of, relay ZAO take over the functions of relay SIMRIA where.

IIECSSSalI'y.

Relay ZAO contact 4(52AO)5 provides a signal path from terminal T to G at the answering set. Each incoming call will thereby ring the telephone set bell while the systemv is in the answer only condition. Relay ZAO contacts 4(2AO)3 and 4(2AO)4 also by-pass switch 4S11 (CU ringup circuit enabling switch) so that the 2-type set can be used for answer only, exclusively, while the CU ringup circuit is enabled. (Refer to Opitional Ringup Circuit below.)

Dicmle and check Operation of the dictate and check button connects the handset to the T1 R1 terminals of the answering set. The dictate relay, 2D, in the CU also operates. The dictate relay performs several functions: it operates contact 2(2D)2 to light the lamp beneath the dictate and check button; breaks the monitor path at opened contact 2(2D)1 of the telephone set to isolate the telephone line from the input circuits (T1 R1) of the answering set. Unless this is done, the subscribers speech, slightly attenuated, will appear on the telephone line and conversely, speech on the telephone line will nd its way to the announcement drum of the answering set. The dictate relay also 4enables the dictate llamp in the answering set to light at the appropriate time by operating contact 4(2D)3.

The dictate lamp circuit of fthe answering set is brought to the control unit so that the lamp will not light unless the dictate and checkV button on the telephone set isdepressed. The scheme is employed to guard against trying to dictate without .first depressing the dictate and check button.

The circuitry of the CU is arranged to permit the dictating and checking of a new announcement on the answering set while the IMR is recording an incoming message. This technique was thought to be desirab-le since. the incoming message may be of long duration and the customer may not want to interrupt the record cycle to change the announcement nor want .to wait an indeterminate interval of time for the record cycle to end.

The subscriber may dictate an announcement during the reco-rd cycle of the IMR but once the record cycle terminates, all subsequent calls will get a dont answer" until the dictate and check button is unlocked, Vby depressing and releasing the A-R reset and restart button. During the time the dictate and check button is locked, the telephone .set ringer will sound with each incoming call; the dont answer alarm signal circuit to the IMR will be closed; the dictate and check button will remain illuminated.

Optional rz'ngup circuit Relays 4RU and 4LSD are included in the control unit to provide an vindependent .r'ingup circuit in the event the subscriber .does not want or need an announcement to precede the IMR record cycle. By operating 451, the CU ringup circuit enabling switch, the system can be made .independent of the answering set.

An incoming call will operate relay 4RU, which enables the operate path of relay 4LSD. The operate path for relay 4RU includes conductor R, switch 431, capacitor 4G25, thermistor 4R1`1, winding of relay 4RU,closed Contact 4(3IMR2)1, operated contact 4(3IMR1A)1, closed contact 4(2AO)6, operated contact 4(4AA,)3, closed contact 4(3VOC5) 1, switch 4S1, closed contacts 4'(2BI)3 and 4(2D)2 and conductor T. Relay 4LSD which is energized by the .operation of contact 4(4RU)1 has a time delay of about 1% seconds. .The telephone line is seized about 1% seconds .after ringing starts; ,the startV beep 'and talk-down .tone are placed on the line after ywhich the caller commences his message, without instructions. 'Once the line has been seized, by operation of 'relay lCPC, the ringup relay 4RU and the line seizure delay relay A4LSD dropout. Since 20-cycle current is necessary 'temperate 4RU again, the r'ingup circuit will remain dormant-until the callV is released and another is;

received.

ing contact 4(4RU)2; The pre-start intervalis a little longer (about 1/2 second) than .the-time delay of relay 4LSD. Relay 4LSDoperates contact 4(4LSD)1 to operate the start relays. 4ST and 4STA, after which relay lCPC seizes the line and releases 4RU and 4LSD from further control activity.

The CU circuits are arranged so that an answering set may be left connected to the CU even though the ringup circuit of the CU is being used. The answering set can thenbe used for answer only service exclusively and not to introduce the incoming message record cycle. CU ringup circuit enabling switch 481 disables the answering set disconnect delay circuit at contact 4 of switch 4S1 and removes the telephone line from the answering set at contacts 4(2AO)3 and 4(2AO)4. 'Except for the omission of the announcement the systemA will display all of the features described herein and will operate as described when the optional ringup circuit of the CU is used in place ofthe answering set..

Pulse-start operation Intermittent shorting of terminals 4R and 4B will pulse-start the telephone answering set or the optional ringup circuit. Closure at these terminals may be accomplished manually or in response to meanssuch as a key telephone set system'which' may, in turn, be energized by ringing current.

With switch 4S1 in theposition shown, relays of the telephone answering set will respond to ground at terminal 1 provided over the path which includes terminals 4B and 4R, operated contact 4(4AA)4, and switch 4S. With switch 4S1 operated', relay 4RU will be operated by power supplied over the path which inclrudesV terminals 4B and 4R, operated contact 4(4AA)4, closed contact 4(2AO)7, switch 4S1, closed contact 4(1CPC)3, winding of relay 4RU, resistor 4R35 and conductor 10.

Talk back, feature The essential characteristic of the talk-back feature is the transmission of the last few seconds of the recorded message back to the caller during the IMRl recording cycle. Talk-back could serve both as a disconnect warning (in lieu of or supplementing the disconnect beep tones) and as a memory jogger.

The answering and recording system employing the talk-back feature would function in the following manner:

1) The caller reaches the equipmetas described in praeious sections; the IMR recording cycle proceeds norm y.

(2) The caller pauses for about two seconds; talkdown tone is placed on the telephone line by the CU.

(3) Caller continues to pause; talk-down tone persists fory approximately eight seconds, at the end of which the IMR receives a signal from the CU. It switches from the record to the reproduce function and back spaces the reproduce transducer on the recording'medium. When the IMR has done this, it signals the CU which performs appropriate switching of the speech and control circuits.

`(4) The last live or six seconds of the callers recorded message is then played back to him at the end of which talk-down tone reappears.

(5) Caller resumes dictating the remainder of his message. 1

This procedure will be followed every time the caller pauses for more than ten seconds. However, to avoid the loss of time-out control, the control circuits will permit only one talk-back cycle for each ten-second pause. If the caller does not resume speaking after talk-back has been completed, the CU will go through a time-out sequence of talk-down tone, disconnect-beeps, and telephone line release.

The

is f

The TMR talk-back yfeature will function as follows: (1) Caller has reached the equipment and is in process of making a recording. He pauses for about two seconds; contact 1(3VOC2A)1 closes and places talk-down tone on the ytelephone line. The IMR stops motion of recording medium by utilizing the signal provided by the CU on vcircuit FM or GM of the` interconnecting cable.

(2) The caller does not talk forranother eight seconds or so. Relay 3VOC3 releases. Release of relay 3VOC3 closes contact 3(3VOC3)3 and connects the CU (ten seconds) disconnect warning signal circuit at terminal T to the IMR control circuit common at terminal M throughv operated contacts 3(3VOC4)2 and 3(4ST)6. The IMR recognizes this signal and switches from the record to reproduce function, baclrspacing the reproduce head at the same time.

(3) Asvthe IMR establishes the reproduce function, it closes the circuit between terminal L (IMR talk-back control circuit) and terminal N (CU control circuit common). Relay 3VOC6 in the control unit operates. l

(4) Operation of relay 3VOC6 enables the IMR talkback speech to reach the telephone line through transformer ITl by way of circuit I and K of the interconnecting cable. The last tive or six seconds of the callers message is transmitted to him.

(5) Operation of relay 3VOC6 disables the voice-operated control section of the CU; relays SVOCI, SVOCZ and SVOCS remain in a non-operated condition; the talk-back speech does not operate'them. Relay 3VOC4 is prevented from releasing by operated contact 3(3VOC6)1 of relay 3VOC6. T alli-down tone and disconnect beeps are also disabled by opened contact 1(3VOC6)1 of relay 3VOC6 in the power supply lead to the tone oscillator.

(6) After talk-back has been completed, the IMR opens the circuit between terminals L and N and relay 3VOC6 releases. Talk-down tone is immediately placed on the telephone line; the voice-operated control circuits are enabled.

(7) if the caller speaks, the talk-down tone ceases; the record cycle continues in the normal manner. If the caller does not speak after talk-back is completed, talkdown tone will continue for four to five seconds, the release time of relay 3VOC4. When relay 3VOC4 releases, the pulse generator and tone generator are enabled; the disconnect beeps are placed on the telephone line. disconnect beeps will continue for about two seconds, lthe release time of relay 4ST. Release of relay 4ST releases relay ICPC; the telephone line is dropped. The IMR record cycle is terminated.

When the talk-back feature is provided, the CU timeout cycle consists of the following sequence:

.-Two seconds-no speech, no talk-down tone, Eight seconds-talk-down tone,

. Six seconds- IMR talk-back speech,

. 'Iwo seconds-disconnect beeps,

. Telephone line release.

This procedure will also be followed if the caller disconnects since the CU cannot distingiush between lack of speech on the telephone line -due to caller pause or caller disconnect, unless caller disconnect is accompanied by an interruption of telephone line current. In cases where disconnect causes an interruption in telephone line current, relay ICPC will release immediately and the IMR record cycle will end without transmission of talk-dow tone, talk-back speech or disconnect beeps.

The caller may interrupt the time-out cycle at any time and establish normal recording conditions except during the talk-back transmission and during transmission of the disconnect beeps. Recapture is permitted, however, duringthe SOO-millisecond (minimum) pause between successive beeps.

The

Automatic Setting of the lime-out e've `The sensitivity of the voice-operated control circuits is adjusted by setting resistor 3R18, so that an incoming voice level, at terminal T and R of the control unit, of

` -45 v.u. would just keep the IMR operating. A lower level would stop the IMR and allow the CU to start the seventeen seconds time-out cycle.v With the -45 v.u. adjustment, room noise at the callers location could easily keep the IMR operating even though the caller is not speaking. nique cannot, therefore, be realized unless the sensitivity `of the voice-operated control circuits is varied automatically to compensate for the eiects of high room noise. When room noise is high, the speech level at which the time-out cycle stops would be increased. Roornnoise is then less likely to start motion of the IMR recording medium or stop the CU time-out cycle.

Room noise could be defined as all audio frequencies v which vary in amplitude (the circuit will not respond to steady state noise signals) except the voice of the caller. Even incidental conversations in the vicinity of the caller could come under the category of noise as well as the usual oscillating fan, oiice equipment noise andy the like. Y It would therefore be diicult for the voiceoperated circuits of the CU to distinguish between nonsteady state noise and low-level speech of the caller.

A way of getting around this diiculty is to switch the IMR start-stop and CU time-out level on the basis of the amplitude of the callers speech at thepcontrol untv terminals. If the lincoming connection is good and the callers` speech level is high, the start-stop and ytime-out level can be raised 10 db or so, thereby reducing the effects of room noise by at least a like amount. Relay 3VOC7, 3R41 and 3G27 are added to the voice-operated control section. Capacitor 3G27 makes relay 3VOC7 slow operate. Resistor 3R41 reduces the gain of the transistor amplier by about l0 db.

If the callers speech'during the incoming message recording cycle is below 25 v.u., relay 3VOC7 does notv the same time, the speech level at which the talk-down toneappears will be raised from -35` v.u. to -25 v.u. For the remainder of the incoming message, the caller will have `to talk about -25 v.u. to talk down the tone and abovev -35 v.u. to keep the IMR operating. After the call is terminated, contact 1(4ST)3 of relay 4ST opens the lookup path of 3VOC7 which then releases and restores the voice-operated circuits to normal.

'Itis to be understood that the above-described arrangements `are illustrative of the application of the principles of the invention. Other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. In ya signal system comprising a line, a voice recorder and means for connecting said line to said recorder and starting the operation thereof to record speech transmitted'over said line, a frequency filter coupled to said line, said filter including means for passing subaudio frequencies corresponding to the syllabic modulation of said speech and suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a predetermined amplitude for a predetermined time interval for stopping the operation of said recorder.

2.In a signal system comprising a line, a voice-recorder and means for connecting said line to said recorderA y Full utilization of the IMR start-stop tech-- @gases-e 1.5 and starting the operation thereof to record speech transmitted over said line, a frequency filter coupled to. said line, said filter including means forpassing subaudio fre:- quencies corresponding to the syllabic modulation of said speech and suppressing allV audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a predetermined amplitude for stopping the operationlof saidrecorder after a first predetermined time interval and disconnecting said recorder from' said line.

operation of saidrecorder. after a `first predetermined time.

interval and disconnectingsaid recorder from said line after a second predetermined time interval, means respon-- sive to said syllabic frequencies wheny the level thereof rises to at least said predetermined amplitude, prior to the expiration of said second predetermined time interval,v

for restarting the operation of said recorder.`

4. In a signal system comprising a line, aV voice recorder and means for connecting said line to said recorder and starting the operation thereof to record speech transmitted over said line, a frequency filter coupled to said line, said filter including means for passing subaudio frequencies corresponding to the syllabic modulation of said speech and suppressing all audio frequencies, meansresponsive to the interruption of transmission of said syl,- labic frequencies for a predetermined time interval for stopping the operation of said recorder.

5. In a signal system comprising a line,. a voice recorder and means for connecting said line to said recorder and starting the operation thereof to record speech trans.-

mitted over said line, a frequency filter coupledV to said.

corder and means for connecting saidfline to said recorderl and `starting the operation thereof to` record speech transimitted over said line, a frequency filter coupled to said line, said filter including means for. passingsubaudio fre'- quencies corresponding to the syllabic modulationofsaid speech and suppressing all audio frequencies, means responsive to. the interruption ofV transmission of said syllabic frequencies for stopping the operation of said recorder after a first predetermined time interval and dis# connecting said recorder from saidV line after a second predetermined time interval, means responsive to the restoration of transmission of said' syllabic frequencies, prior to the expiration of-said second predetermined. time interval, for restarting the operation of said recorder.

7. In a signall system comprising a line, a voice recorder and means for connecting said line to said recorder and starting the operation thereof to recordspeech transi mitted over said: line, a frequency filter coupledto said line, said filter includingy means for passing subaudio frequencies corresponding tothe syllabic modulation of said speech and suppressing. all yaudio frequencies, a signal tone generator coupled to said line for transmitting an audible signal thereover, and means energized' by said syllabic frequencies' when-the level thereof is above a predetermined ,amplitude for rendering said generator'inoperative-totransmit said signal Ya Y Si In a signal' system comprising a line', a signal tone generatorl and a voice-operated control means, meansy for coupling said generator to said line; means'for coupling said voice-operated control meansto said line', means'for transmitting speechV over said line, Vsaid voiceoperated control meanscomprising afrequency Vfilter, said filter including means for passing subaudio frequencies corresponding to the syllabic modulation of said: speech and suppressing all audiov frequencies; meansr responsive to said syllabic frequencies' when the level thereoffi's below a predetermined' amplitude for renderingsaid" generator operative to transmit a signal tone over said line.

9. In a signal system comprisingA a line, a voice recorder and means for connectingsaid line to said recorder and starting the operation thereof to record Speechtransmitted over said line, a frequency filter coupled to said line, said filter including means'for passing subaudio frequencies corresponding tothe syllabic modulation of said' speech and suppressing all audio frequencies, a signal tone generator coupled to said line for transmitting an audible signal thereover, and means responsive to the interruption of transmission of said syllabic frequencies for rendering said generator operative to transmit said signal.

10; in al signal system comprising a line, a voice recorder and means for connecting' said line to` said recorder and starting the operation thereof to record speech transmitted over said line, a frequency filter coupled to said line, said filter including means for passing suoaudioy frequencies corresponding tothe syllabic modulation ofsaid speech and suppressing all audio frequencies, a signal tone generator coupled to said line for transmitting an audible signal thereover, means responsive to thel interruption of' transmission of said syllabic frequencies for stopping the `operation of said recorder andrendering said generator operative to transmit said signal after a first predetermined timeinterval and: disconnecting said signal tone generator and recorderl from said line after a secondpredetermined time interval.

l1. A signal system in accordance with clairnlO includ'- ingmeans responsive to the restoration 'of transmission of said syllabic frequencies, prior to thev expiration of said" second predetermined time interval, for restarting the operation of said recorder.

l2. In a signal system comprising av line, a voice recorder and means for connecting said line to said recorder and starting the operation thereof to record' speech transmitted over said line, a frequency filter coupledV to `Said line, said filter including means for passing subaudio frequencies corresponding to the syllabic modulation of said speech and suppressing'alll audio' frequencies, a signal tone generator coupled' to said line for transmitting an audible signal' thereover, means respon*- sive to said syllabic frequencies when the level'thereof falls below a predetermined amplitude for` stopping the `operation of said recorder and rendering said generator operative to transmit said signal and, after a predetermined time interval, disconnecting said signal ton-e generator and recorder from said line.

13. A signal system in accordance with claim l2 includingv means responsive to said syllabic frequencies when the level thereof risesl toat least said predetermined amplitude, prior tothe expiration of saidpredetermined time interval, for restarting the operation' of said recorder.

14. An automaticteleplrone message recordingl system comprising a` telephoneV line, a recorder, means for connecting said' telephone. line tol said recorder' and' starting the operation thereof to record a message transmitted over said line, a frequency filter coupled to said line, said lter including means for passing subaudio frequencies corresponding to the syllabic modulation of said message and suppressing all audio frequencies, a signal tone` generator'coupledto said line for transmittingran' audible. signal thereover, means responsive to said syllabic frequencies `when the level thereof falls below'a first predetermined amplitude for rendering said generator operativeto transmitv said signal, means responsive to said syllabic frequencies when the level thereof falls below a second predetermined amplitude for stopping the operation of said recorder.

15. An automatic telephone message recording system comprising a telephoneV line, a recorder, means for connecting said telephone line to said recorder and-starting the operation thereof to record a message transmitted over said line, a frequency filter coupled to said line, said filter including means for passing subaudio frequencies corresponding to the'syllabic modulation of said message and suppressing all audio frequencies, a signal tone generator coupled to said line for transmitting an audible signal thereover, means responsive to said syllabic frequencies when the level thereof falls below a first predeterminedamplitude for rendering said generator operative to transmit said signal, -means responsive to said syllabic frequencies when the level thereof falls below a second predetermined amplitude lfor stopping the operation of said recorder and, after a predetermined time interval, disconnecting said signal tone generator and recorder from said line.

16. A signal system in accordance with claim 15 including means responsive to said syllabic frequencies when the level thereof rises to at least said second predetermined amplitude, prior to the expiration of said predetermined time interval, for restaiting the operation of said recorder.

17. In a signal system comprising a line, a signal tone generator, a voice recorder, a voice-operated control means and input terminals for said line, a first transformer for coupling said recorder and said voice-operated control means to said line, a second transformer disposed between said first transformer and said terminals for coupling said generator to said line, means for transmitting speech over said line, said voice-operated control means comprising a frequency filter, said filter including means for passing -subaudio frequencies corresponding to the syllabic modulation of said speech and suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a predetermined amplitude for rendering said generator operative to transmit a signal tone over said line, an impedance network tuned to said tone disposed between said first and second transformers for attenuating the level of said signal tone transmitted to said recorder.

18. In a signal system comprising a line, a signal tone generator, a voice recorder, a voice-operated control means and input terminals for said line, a first transformer for coupling said recorder and said voice-operated control means to said line, a second transformer disposed between said first transformer and said terminals for coupling said generator to said line, means for transmitting speech over said line, said voice-operated control means comprising a frequency filter, said filter including means for passing subaudio frequencies corresponding to the syllabic modulation of said speech and suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a first predetermined amplitude for rendering said generator operative to transmit a signal tone over said line, means responsive to said syllabic frequencies when the level thereof is below a second predetermined amplitude for a predetermined time interval for disconnecting said recorder from said line.

19. A signal system in accordance with claim 18 including an impedance network disposed between said first and second transformers for attenuating said signal tone.

20. A signal system in accordance with claim 18 including amplifying means disposed between said first and second transformers for amplifying said speech.

21. In an automatic telephone message recording system comprising a telephone line, a recorder, a voiceoperated control means, and a signal tone generator,

'as-lass y means responsive to a signal transmitted over said line for coupling said recorder, control means and generator to said line and for conditioning said recorder to record a message transmitted over said line, said voice-operated control means comprising afilter for passing subaudio frequencies corresponding to the syllabic modulation of said message and for suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a first-predetermined amplitude for rendering said generatoroperativev to transmit said tone over said line-means responsive to said syllabic frequencies when the level thereof is below a second predetermined amplitudev for a predetermined time interval for disconnecting said` recorder, control means and generator from said l-ine. n

22. In an automatic telephone message vrecording system comprising a telephone line, a recorder and a voiceoperated control means, means responsive to a signal transmitted over said line for coupling said recorder and control means to said line and for conditioning said recorder to record a message transmitted over said line, said voice-operated control means comprising a filter for passing subaudio frequencies corresponding to the syllabic modulation of sai-d message and for suppressing all audio frequencies, control means in said recorder for starting and stopping the operation thereof, said control means being responsive to said syllabic frequencies in such manner as to stop the operation of said recorder for the time interval during which the level of said frequencies is below a predetermined amplitude and to restart the operation of said -recorder when the level of said frequencies rises to said predetermined amplitude.

23. In an automatic telephone message recording system comprising a telephone line, a recorder, and a voiceoperated control circuit, means for coupling said recorder and control circuit to said line and conditioning said recorder to record a message transmitted over said line, said recorder comprising means for reproducing and playing back said recorded message, said control circuit comprising a filter for passing subaudio frequencies corresponding to the syllabic modulation of said message and suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below -a predetermined amplitude for stopping the operation of said recorder, and, after a predetermined time interval, conditioning said recorder to play back a predetermined portion of said recorded message over said line.

24. In an automatic telephone message recording system comprising a telephone line, a recorder, -a voiceoperated control circuit and a signal tone generator, means for coupling said recorder, control circuit and generator to said line and conditioning said recorder to record a message transmitted over said line, said recorder comprising means for reproducing and playing back said recorded message, said control circuit comprising a filter for passing subaudio frequencies corresponding to the syllabic modulation of said message and suppressing all audio frequencies, means responsive to said syllabic frequencies when the level thereof is below a predetermined amplitude for stopping the operation of said recorder and rendering said generator operative to transmit said tone over said line, and, :after a predetermined time interval, conditioning said recorder to play back a predetermined portion of said recorded message over said line and rendering said generator inoperative.

25. In a signal system comprising a line, and a voiceoperated control circuit, means for coupling said control circuit to said line, means for transmitting speech over said line, said voice-operated control circuit comprising a filter for passing subaudio frequencies corresponding to the syllabic modulation of said speech and for suppressing all audio frequencies, an amplifier in said control circuit disposed between said line coupling means and said filter, means responsive to said syllabic frequencies 19 when the level thereof is above a predetermined amplitude for reducing the gain of said amplifier.

26. In an automatic .telephone message recording system comprising a telephone line, a recorder, a voiceoperated control circuit, a signal tone generator and input terminals for said line, first coupling means for coupling said recorder and said control circuit to said line, second coupling means disposed between said first coupling means and said terminals for coupling said generator to said line, means for transmitting a message over said line and conditioning said recorder to record said message, said voice-operated control circuit comprising a filter for passing subaudio frequencies corresponding to the syllabic modulation of said message and suppressing all audio frequencies, an amplier disposed between said rst coupling means and said filter, means responsive to vsaid syllabic frequencies when the level thereof is below a first predetermined amplitude for rendering said generator operative to transmit a signal tone over said line, means responsive to said syllabic frequencies when the level thereof is below a second predetermined amplitude for a predetermined time interval for disconnecting said recorder from said line, means responsive to said syllabic frequencies when the level thereofis above a third predetermined amplitude for reducing the gain of said amplier. f Y- Y 27. An automatic telephone message recording system in accordance wi-th claim 26 including -an impedance network disposed between said first and second coupling means for attenuating the level of said signal tone transmitted to said recorder.

28. An automatic telephone message recording system in accordance with claim 26 including an amplifier disposed between said rst and second coupling means for amplifying said message transmitted to said recorder and said voice-operated control circuit.

References Cited in the le of this patent UNITED STATES PATENTS 

